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00001 /* ****************************************************************** **
00002 **    OpenSees - Open System for Earthquake Engineering Simulation    **
00003 **          Pacific Earthquake Engineering Research Center            **
00004 **                                                                    **
00005 **                                                                    **
00006 ** (C) Copyright 1999, The Regents of the University of California    **
00007 ** All Rights Reserved.                                               **
00008 **                                                                    **
00009 ** Commercial use of this program without express permission of the   **
00010 ** University of California, Berkeley, is strictly prohibited.  See   **
00011 ** file 'COPYRIGHT'  in main directory for information on usage and   **
00012 ** redistribution,  and for a DISCLAIMER OF ALL WARRANTIES.           **
00013 **                                                                    **
00014 ** Developed by:                                                      **
00015 **   Frank McKenna (fmckenna@ce.berkeley.edu)                         **
00016 **   Gregory L. Fenves (fenves@ce.berkeley.edu)                       **
00017 **   Filip C. Filippou (filippou@ce.berkeley.edu)                     **
00018 **                                                                    **
00019 ** ****************************************************************** */
00020                                                                         
00021 // $Revision: 1.1.1.1 $
00022 // $Date: 2000/09/15 08:23:17 $
00023 // $Source: /usr/local/cvs/OpenSees/SRC/analysis/integrator/ArcLength.h,v $
00024                                                                         
00025                                                                         
00026 // File: ~/analysis/integrator/ArcLength.h
00027 // 
00028 // Written: fmk 
00029 // Created: 07/98
00030 // Revision: A
00031 //
00032 // Description: This file contains the class definition for ArcLength.
00033 // ArcLength is an algorithmic class for perfroming a static analysis
00034 // using the arc length scheme, that is within a load step the follwing
00035 // constraint is enforced: 
00036 //  i=1        delta U^T delta U + alpha^2 delta lambda^2 = delta s^2
00037 //  i>1        dU^T delta U + alpha^2 dLambda delta lambda = 0
00038 // where dU is change in nodal displacements for step, dLambda is
00039 // change in applied load and arcLength is a control parameter.
00040 //
00041 // What: "@(#) ArcLength.h, revA"
00042 
00043 #ifndef ArcLength_h
00044 #define ArcLength_h
00045 
00046 #include <StaticIntegrator.h>
00047 
00048 #include <LinearSOE.h>
00049 #include <AnalysisModel.h>
00050 #include <FE_Element.h>
00051 #include <Vector.h>
00052 
00173 class ArcLength : public StaticIntegrator
00174 {
00175   public:
00178     ArcLength(double arcLength, double alpha = 1.0);
00179 
00180 
00185     ~ArcLength();
00186 
00187 
00196     int newStep(void);    
00197 
00209     int update(const Vector &deltaU);
00210 
00220     int domainChanged(void);
00221 
00222     
00229     int sendSelf(int commitTag, Channel &theChannel);
00230 
00237     int recvSelf(int commitTag, Channel &theChannel, 
00238 
00239     FEM_ObjectBroker &theBroker);
00240 
00245     void Print(ostream &s, int flag =0);    
00246 
00247     
00248   protected:
00249     
00250   private:
00252     double arcLength2;
00253 
00255     double alpha2;
00257     Vector *deltaUhat, *deltaUbar, *deltaU, *deltaUstep;
00259     Vector *phat; 
00260     double deltaLambdaStep, currentLambda;
00262     int signLastDeltaLambdaStep;
00263 };
00264 
00265 #endif
00266